[PATCH v10 10/10] PCI: Introduce pci_remap_iospace() for remapping PCI I/O bus resources into CPU space

[Liviu Dudau <Liviu.Dudau@arm.com>]

Introduce a default implementation for remapping PCI bus I/O resources
onto the CPU address space. Architectures with special needs may
provide their own version, but most should be able to use this one.

Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rob Herring <robh+dt@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
---
 drivers/pci/pci.c             | 33 +++++++++++++++++++++++++++++++++
 include/asm-generic/pgtable.h |  4 ++++
 include/linux/pci.h           |  3 +++
 3 files changed, 40 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 2c9ac70..654b44c 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2704,6 +2704,39 @@ int pci_request_regions_exclusive(struct pci_dev *pdev, const char *res_name)
 }
 EXPORT_SYMBOL(pci_request_regions_exclusive);
 
+/**
+ *	pci_remap_iospace - Remap the memory mapped I/O space
+ *	@res: Resource describing the I/O space
+ *	@phys_addr: physical address where the range will be mapped.
+ *
+ *	Remap the memory mapped I/O space described by the @res
+ *	into the CPU physical address space. Only architectures
+ *	that have memory mapped IO defined (and hence PCI_IOBASE)
+ *	should call this function.
+ */
+int __weak pci_remap_iospace(const struct resource *res, phys_addr_t phys_addr)
+{
+	int err = -ENODEV;
+
+#ifdef PCI_IOBASE
+	if (!(res->flags & IORESOURCE_IO))
+		return -EINVAL;
+
+	if (res->end > IO_SPACE_LIMIT)
+		return -EINVAL;
+
+	err = ioremap_page_range(res->start + (unsigned long)PCI_IOBASE,
+				res->end + 1 + (unsigned long)PCI_IOBASE,
+				phys_addr, pgprot_device(PAGE_KERNEL));
+#else
+	/* this architecture does not have memory mapped I/O space,
+	   so this function should never be called */
+	WARN_ON(1);
+#endif
+
+	return err;
+}
+
 static void __pci_set_master(struct pci_dev *dev, bool enable)
 {
 	u16 old_cmd, cmd;
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 53b2acc..977e545 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -249,6 +249,10 @@ static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
 #define pgprot_writecombine pgprot_noncached
 #endif
 
+#ifndef pgprot_device
+#define pgprot_device pgprot_noncached
+#endif
+
 /*
  * When walking page tables, get the address of the next boundary,
  * or the end address of the range if that comes earlier.  Although no
diff --git a/include/linux/pci.h b/include/linux/pci.h
index a494e5d..fc8c529 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1100,6 +1100,9 @@ int __must_check pci_bus_alloc_resource(struct pci_bus *bus,
 						  resource_size_t),
 			void *alignf_data);
 
+
+int pci_remap_iospace(const struct resource *res, phys_addr_t phys_addr);
+
 static inline dma_addr_t pci_bus_address(struct pci_dev *pdev, int bar)
 {
 	struct pci_bus_region region;
-- 
2.0.4